1,721,075 research outputs found
Analysis code for publication: 'The aperiodic exponent of subthalamic field potentials reflects excitation/inhibition balance in Parkinsonism'
No full textThe analysis code is written for MATLAB, and version 2020b was used for the associated publication.
This code analyses the rat data with respect to aperiodic component changes during high and low STN spiking states, and the human data ON and OFF levodopa and deep brain stimulation. It generates Figures 1 to 3 of the corresponding article entitled 'The aperiodic exponent of subthalamic field potentials reflects excitation/inhibition balance in Parkinsonism'.
The master script (Master_Script.m) will generate Figures 1-3. Within every function, sub-sections are commented
Local Field Potential (LFP) data recorded from externalized Essential Tremor DBS Patients during 3 upper-limb movement tasks
No full textThis dataset was recorded during sessions with externalized Deep Brain Stimulation (DBS) Essential Tremor (ET) patients. Patients were asked to perform a pegboard insertion task, a posture hold with arms stretched out front, and a rice pouring task between two cups. Data was recorded both with DBS stimulation on and off. Here we only provide a brief description and refer to the Methods section of [1] for further details on the patients (incl. clinical information), hardware, and recording setup.
The dataset is structured as a series of 8 folders (ET1, ET2, …, ET8), with each folder corresponding to data recorded from an individual patient. Each of these folders contains HDF5 files named _.h5 (e.g. Pegboard_on.h5), where each file consist of arrays containing bilateral, multi-channel LFPs under the “LFP” key and a corresponding movement label under the “label” key. Movement labels were extracted from EMG and accelerometer data attached to the arms and hands of patients. The LFP data comes highpass-filtered (4th order, one-pass butterworth filter with cut-off frequency of 1 Hz). The sampling rate for all datasets is 2048 Hz.
This dataset has been set up to directly work with the code provided at https://github.com/fer-rplazas/feature-extraction-methods, which includes utilities to load the data, train models with it, and generate figures
Subthalamic and thalamic local field potential recordings from patients with cervical dystonia
No full textThis data set contains data that were used in Wiest et al., 2022 (https://doi.org/10.1002/mds.29302).
The files are in MATLAB .mat format.
Local field potentials (LFPs) were recorded from 7 patients with cervical dystonia (non-directional Boston Vercise leads with 8 contact levels, placed in the subthalamic nucleus, Zona incerta and ventrolateral thalamus). 5 patients were recorded bilaterally, yielding 12 hemispheres.
All channel labels are saved in SmrData.WvTits. LFPs were recorded from contact levels adjacent to the stimulation contact in bipolar fashion (label e.g. L13 if L2 was stimulated). All other LFPs were recorded in unipolar mode with common mode rejection (label e.g. L4). In addition, selected electroencephalography (EEG) contacts were recorded with common mode rejection (label e.g. C3). In some patients, electromyography (EMG, e.g. left splenius muscles (SplL) or left sternocleidomastoid muscle (SCML)) from dystonic neck muscles and accelerometer data (from the forehead or the vertex) were recorded. The time stamps and intensity of the applied stimulation currents are saved in channel Cur1/Am1.
In this dataset, we progressively increased stimulation intensity in steps of 0.5 mA until either the side effect threshold or 4.5 mA were reached. We tested all middle contacts (levels 2 to 7 if leads are labelled from 1 to 8) in this way.
In Participants 5 to 7, we applied single pulse stimulation (25 pulses) to all 8 contact levels in sequence (file name e.g. P6_Right_Single.mat)
STN local field potential recordings from awake patients with Parkinson’s, ON and OFF meds, and during 130 Hz DBS
No full textSubthalamic local field potential recordings from awake patients with Parkinson’s disease while leads were externalised. In 30 hemispheres, this data was recorded ON and OFF dopaminergic medication and in 26 hemispheres before and during 130 Hz deep brain stimulation of the subthalamic nucleus.
DBS data:
This file contains data from 26 hemispheres. The sampling rates of the respective files can be found in MATRIX_DBS.fs. MATRIX_DBS.signal_base contains subthalamic local field potential data at rest. MATRIX_DBS.signal_dbs contains subthalamic local field potential data during 130 Hz deep brain stimulation of the subthalamic nucleus as described in the corresponding article.
Medication data:
This dataset was recorded for 30 hemispheres ON and OFF levodopa. Each file has more information on how the data is arranged: SmrData.WvTits. Channel titles denote EEGs (e.g. Fz, Cz, F3), bipolar LFP channels (e.g. Le02, R02, L13) or accelerometer data (e.g. AcX, AcY)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Neuronal dynamics of flexible motor control in the human subthalamic nucleus and cortex
Full text linkBeta and gamma oscillations have long been associated with motor control, with beta generally assumed to be anti-kinetic and gamma pro-kinetic. This thesis aims to link these oscillations to several components of flexible motor control: inter-limb coordination, sensorimotor synchronization, abrupt stopping and regulation of the extent and speed of muscle contractions. The subthalamic nucleus (STN) plays an important role in controlling movements. In three separate experiments, I recorded local field potentials from the STN in Parkinsonâs disease patients on dopamine replacement therapy after they underwent deep brain stimulation surgery. In one task, EEG recordings were also obtained from healthy participants. In a stepping-in-place paradigm, STN beta oscillations were modulated relative to the contralateral step cycle, indicating segregated processing of the left and right limb in the contralateral STN at beta frequencies. Beta modulation was enhanced when auditory cues were provided and sensorimotor synchronization improved. During rhythmic finger tapping and sudden stopping, beta oscillations were again modulated. If post-movement beta was relatively high shortly before participants heard the stop signal, stopping was more successful. I hypothesize that post-movement beta reflects either evaluation of the motor plan according to sensory feedback from the last finger tap or processing related to timing adjustments in the next movement. In both cases, low post-movement beta suggests active neural processing and less reserve for stopping. The main correlate of successful stopping during the actual inhibition process directly following the stop signal, however, was a gamma power increase. Finally, both gamma and beta oscillations were modulated during motor imagery of three different force levels, indicating that their levels reflect motor vigour even in the absence of proprioceptive feedback and may be used as neurofeedback or BCI control signal. Altogether, these findings suggest that beta oscillations reflect wider motor control functions than just being anti-kinetic. Conversely, STN gamma oscillations do not only have a pro-kinetic role, as widely perceived, but are important for abrupt action stopping as well.</p
The functional role of theta-gamma oscillations in human motor neurophysiology
Full text linkBACKGROUND: Motor cortical theta-gamma (θγ) oscillations have recently gained the attention of neuroscientific literature following recent results from Akkad et al. (2021) in which artificially entraining 75Hz γ oscillations, phase amplitude coupled to the positive half of a 6Hz θ envelope (θγ peak; TGP) using transcranial alternating current stimulation (tACS) significantly modulated motor behaviour. Such an effect was not seen when entraining 75Hz γ oscillations, phase amplitude coupled to the negative half of a 6Hz θ envelope (θγ trough; TGT). There is a limited understanding of the neurophysiological mechanisms underpinning such behavioural effects. To this end, this thesis explored the effects of θγ oscillations on healthy human motor learning behaviour, TMS metrics of receptor-mediated inhibition and excitation, and MRI-measured functional connectivity within the sensorimotor network. Taken together, these results provide novel insights into the neurophysiological mechanisms underlying human motor cortical θγ oscillations and showcase the potential of driving such oscillations on noninvasively modulating healthy human motor neurophysiology.
METHODS: I artificially entrained motor cortical θγ oscillations using tACS. Depending on the research question of each experiment, I delivered different types of θγ oscillations (e.g. 45Hz versus 75Hz TGP waveforms or TGP versus TGT). I also investigated two different potential mechanisms of action for tACS: entrainment (delivering three second bursts of tACS) versus neuroplasticity (delivering 20 minutes continuous tACS).
EXPERIMENT 1: I first investigated whether the positive behavioural effects reported by Akkad et al. (2021) were frequency-specific. I compared the effects of driving 45Hz versus 75Hz γ TGP on motor behaviour. The tACS was delivered in a movement-locked manner, such that participants only received three seconds bursts of tACS per three seconds trial. I found that participants receiving 45Hz TGP tACS hit significantly fewer targets than participants receiving sham tACS. I found no significant difference in the number of targets hit between participants receiving 75Hz TGP tACS and sham tACS. This was unexpected, given the previously reported behavioural effect of 75Hz TGP tACS on motor behaviour (Akkad et al., 2021). This suggests that short bursts of 75Hz TGP tACS potentially engages different neurophysiological mechanisms than longer stimulation periods. Furthermore, I found that that these same participants receiving 45Hz TGP tACS had significantly reduced force outputs compared to participants receiving sham tACS, as quantified by extracting the slope of the first instance of force production. Overall, these results suggest that 45Hz TGP tACS impedes behavioural gains, potentially via reductions in force output.
EXPERIMENT 2: Next, I investigated the phase-specific effects reported by Akkad et al. (2021) such that TGP, and not TGT, significantly modulated motor behaviour. Given the relationship between motor learning and GABA, it is possible that TGP uniquely modulates GABA. Here, using Transcranial Magnetic Stimulation (TMS), I sampled single and paired-pulse TMS to assess cortical excitability and receptor-mediated inhibition and excitation before, during, and after 20 minutes of continuous 75Hz TGP tACS. I found that TGP significantly reduced extrasynaptic GABAergic tone, serving to explain the positive behavioural findings of Akkad et al. (2021).
EXPERIMENT 3: Finally, I investigated whether the positive behavioural effects of TGP tACS reported by Akkad et al. (2021) were mediated by local changes in neuronal activity or by wider, network level changes in sensorimotor network functional connectivity. Using a combined tACS-functional MRI approach, I compared the effect of TGP tACS on sensorimotor functional connectivity at rest versus during motor learning. I found that TGP tACS significantly reduced the functional connectivity between the sensorimotor network and the right somatosensory cortex from pre- to late-tACS during motor learning. I also found that TGP tACS significantly increased the functional connectivity between the sensorimotor network and the right supramarginal gyrus from late- to post-tACS during motor learning.
DISCUSSION: Together, the findings of the present studies address the different facets of the complex neurophysiological mechanisms of motor cortical θγ oscillations in healthy human motor behaviour
- …
